Dear developers,
I am trying to calculate the eliashberg function for a variety of systems. However, the harmonic approximation often fails in these systems generating negative frequencies. How do I generate higher order IFCs that can later be used with the EPW module to calculate the eliashberg function?
Hi Nikitha,
You can use the ZG module of the EPW (see EPW 2023 paper) to compute anharmonic force constants. Using the anharmonic force constants with the harmonic dvscf you can use it for Eliashberg calculations. For the anharmonic special displacement method, see the 16:15-17:45 tutorial on Friday:
https://epw2024.oden.utexas.edu/74-schedule.
For the use of Eliashberg expressions in EPW with anharmonic corrections using ZG code, please have a look at the following papers
https://doi.org/10.1038/s41524-025-01818-9
https://arxiv.org/abs/2510.25902
https://doi.org/10.1039/D5TC02600H
Regards,
Shashi